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Jay
Jay, Certified Infiniti Technician
Category: Infiniti
Satisfied Customers: 19492
Experience:  20+years, Nissan and Infiniti experience and currently now working for a Infiniti Dealer
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1999 G20: car jerks..constant speed..automatic with 173,000 miles

Resolved Question:

When desired speed is achevied, the car jerks when trying to maintain constant speed. I have a 1999 G20 4 door automatic with 173,000 miles.
Submitted: 4 years ago.
Category: Infiniti
Expert:  Jay replied 4 years ago.
Hello and Thank you for using JustAnswer.com

Do you have a Check Engine light on when the car is running?

Let me know, Thanks Jay!
Customer: replied 4 years ago.
It's always on. The last time we had it checked, it read injector problem, but engine runs fine. The only time I have an engine idle problem is when I get gas and start the car back up it chugs.
Expert:  Jay replied 4 years ago.
Do you happen to know the code number you have?
Customer: replied 4 years ago.
no, but have been told injector
Expert:  Jay replied 4 years ago.
Does fuel system lean or fuel system rich sound familar?
Customer: replied 4 years ago.
never mentioned............what would that have to do with the constant speed jerking? Just asking
Expert:  Jay replied 4 years ago.
Cause those codes are normally caused by the MAF sensor. That can cause your Jerking.

the MAF ( Mass Air Flow ) sensor heated element which meters the air so the computer can add the proper fuel mixture has fallen out of spec. If it causes a Service Engine Soon light it can be because the Air and fuel Mixture is so off that it could cause lean or rich codes, or simply MAF sensor codes. When it's bad it can cause No Start, Stalling, poor acceleration, won't rev over a certain Rpm, and running issues. I would have the Air and Fuel mixture readings checked to verify. Checking the voltage will not show the fault, the air and fuel mixture will. If found to be bad, do not replace with a After Market one. After market MAF sensors never seem to work properly. There heated element doesn't work right which can cause 02 sensors to flat line and have you chasing you tail trying to figure out what is wrong. So the only way to correct this issue if you do have a bad MAF sensor is to replace it with a OEM.

If you have any more questions on this, please feel free to ask. Thanks Jay!

Jay and 4 other Infiniti Specialists are ready to help you
Customer: replied 4 years ago.
I am not experincing "No Start, Stalling, poor acceleration, won't rev over a certain Rpm". Just running issues. How much is an MAF sensor? Where is that located, in the block or elsewhere?
Customer: replied 4 years ago.
,I am not experincing "No Start, Stalling, poor acceleration, won't rev over a certain Rpm".  Just running issues.  How much is an MAF sensor?  Where is that located, in the block or elsewhere?
Expert:  Jay replied 4 years ago.
Those are just some symptoms it can cause. The MAF sensor is around 300 from the dealer.

Thanks Jay!
Jay and 4 other Infiniti Specialists are ready to help you